Dental impression materials are used to record the oral situation of a patient. The resulting hardened impression material captures the negative of the oral situation.
Most dental impression materials are delivered in a two or more paste form, containing a base paste and a catalyst paste, which are mixed prior to their application. The mixed pastes are typically applied with the help of a dental tray and/or a syringe-type device. Usually the hardened material can be removed after about one to about six minutes after application. The hardened impression material is used either for making a provisional restoration using a temporary crown and bridge material or for producing a positive model of the oral situation by casting the mould with e.g. gypsum. The obtained positive model is used for making the final restoration in the dental laboratory.
Different types of chemistry can be employed to formulate impression materials. Often used are polyether impression materials which cure by a cationic ring-opening polymerization of aziridines (e.g. Impregum™, 3M ESPE), polysiloxanes which cure via a hydrosilation reaction (e.g. Imprint™, 3M ESPE), polysiloxanes which cure via a condensation mechanism (e.g. Xantropren™, Heraeus Kulzer), mixtures of polyethers and siloxanes which cure via a hydrosilation mechanism (e.g. Senn™, GC) and polyethers which cure via a condensation mechanism (e.g. P2™, Heraeus Kulzer).
To achieve a pasty consistency of the catalyst and the base paste, fillers are typically added. The fillers can also be used to adjust the rheology of the uncured paste.
An improved tensile strength can be desirable to avoid tearing of the set impression material. Tearing of the set impression material may result in loss of information about the clinical situation.
US 2004/0149164 relates to a mixture of elongated N-alkylaziridine prepolymers which can be used as a dental material. The mixture can contain various modifiers like finely divided fillers, pigments, thixotropic agents and surface-active substances.
U.S. Pat. No. 6,599,960 relates to storage-stable cationically polymerzed preparations with improved hardening characteristics. The preparations can contain 0.0005 to 50 wt.-% of soluble and/or fine-particle organic and/or inorganic alkaline earth and/or alkali metal compounds. The preparation can be used for making dental impressions.
U.S. Pat. No. 3,453,242 describes elastomers from polyethers and ethylene imine derivatives. The ethylene imine compouind is subjected to a cross-linking reaction by means of such cross-linking agents as esters of strong acids.
WO 2007/143490 refers to a composition comprising a prepolymer comprising aziridino groups and being characterized by a certain equivalent weight, a crosslinker and an initiators, optionally filler(s) and additive(s). The composition can be used for coating, sealing, moulding, adhering, making impressions and for producing a dental material.